# Questions tagged [moment]

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### Why isn't the moment always included in a free-body diagram?

Now I have seen many times both in my physics book and other books when drawing a free body diagram the moment is not included but the forces are. For example in 2d when a beam is fixed to a wall ...
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### What is the connection between moments in probability theory and the moment of inertia?

My question arises as the moment of inertia (MOI) has been described as a second moment. In my understanding if the MOI is indeed a second moment of a distribution of mass, this suggests the MOI could ...
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### Mass moment of inertia flipping in different mediums

Consider someone performing a front flip in the water versus in the air. Assume the body position in both cases to be identical. In which case would the mass moment of inertia be greater and why? Prof ...
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### Average Energy and Magnetization of One Site Hubbard Model

I have been trying to implement the exercises from Section 2 part B (for which $t = 0$, and only considering the effects of U) given in this set of lecture notes - Numerical Studies of Disordered ...
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### Calculate bending moment for cantilever with uniformly distributed load

I am trying to understand how to calculate the bending moment for a cantilever with a uniformly distributed load so that I can build an equation of moments, as shown in this example: I tried ...
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### Moment of inertia of a cantilever beam [closed]

As part of a project, I'm calculating deflection of a cantilever beam, something like the image below where the beam bends due to a load. To do so requires its moment of inertia, and I'm thinking of ...
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### Misconception About Torque Log cutting example

LOG CUTTING "Three friends go camping in the forest with their families. They start collecting wood to make a fire. They find a large, branchless log in the forest. One end of the log is very ...
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1 vote
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### Sign of distance/arm when finding moment/torque

I know that $M=Fd$, but when I have a negative moment, does the sign of the moment matter when I'm calculating for distance? If yes, then what would it mean when distance is negative?
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### i've been told that a motor bike can turn on a frictionless horizontal surface by leaning towards the horizontal

their reasoning was that when the bike lean towards horizontal the reaction acting on the bike by surface will act in an angle through the center of gravity of the slanted bike(not perpendicular to ...
407 views

### Difference between moment and couple

What is the exact difference between a moment and a couple? In some YouTube channels and books, they say the moment of a force produces a translational as well as rotational motion whereas the concept ...
68 views

### Underwater chests in video games

Many video games creators put chests with items in various places. Sometimes the chests can be found underwater. Here are two examples: Dying Light 2 Shadow of the Tomb Raider However, I started ...
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### What is the most fundamental reason for introduction of force moment $\vec{M}=\vec{r}\times\vec{F}$? [duplicate]

Force moment is defined as $\vec{M}=\vec{r}\times\vec{F}$ when force is perpendicular to the lever arm. How do we know that it has to be this way? How do we know it is not $F\cdot r^2$ etc. ? My ...
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### How does a lever arm increase force?

A lever and a fulcrum is able to to multiply the input force to the output force and trade moving distance for increased force. The same happens in automobile transmissions, taking advantage of high ...
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### Why does moment/torque equal to force multiplied by distance?

moment is equal to force x distance but why is is it so. why is it so that greater the distance less the effort needed? i tried understanding it mathematically but it just went over my head. if any ...
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### How do you apply a pure torque?

A pure torque does not have a point of application. For example, in the beam shown below, the reactions are same regardless of the torque placement: But how do you apply torque in reality? For ...
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### If torque is a form of moment, then why is the word 'moment' used for the 'magnetic dipole moment', NiA, for a current-carrying loop?

I thought torque is a form of moment: If the moment makes the object rotate, we call it torque; otherwise we just use the name moment. However it seems the electric & magnetic dipole moments are ...
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### Maintaining the balance of a rod of uniform density [closed]

Assume a rod which: is of uniform density $\rho$. is a metre long. The rod is balanced on a knife edge at 58 cm. mark (in the notation where the extreme left side is assumed to be 0). To the extreme ...
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### How non-collinear forces balance each other?

In the system of parallel forces , all the forces are non-colinear. So how to they balance each other?. Here in this case a wooden plank is supported at its end by two supports. All the forces here ...
618 views

### Are there physics theorems that can prove maths theorems? Eg Pythagoras' Theorem

There's this recent post on maths overflow Which theorems have Pythagoras' Theorem as a special case? that has an answer by dxiv that appears to use a physics theorem to a prove a maths theorem, ...
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### Overturning torque on a car navigating a curve

The car shown above with mass M is turning to the left with an uniform angular speed W on a circular path with radius R. When the angular speed is increased to a critical value C, one of the normal ...
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### How is there moment for a group of forces which its resultant equals zero?

I am a beginner in mechanics, and when I was introduced to moments there was a theorem that says "if a set of forces acting on a rigid body has a resultant, then the algebraic sum of these forces ...
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### Dipole Moment: what does it really represent?

Wikipedia gives the most general expression for the $n^{\rm th}$ moment $\mu_n$ of a physical quantity $\Lambda$ as: $$\mu_n = \int {\bf x}^n \space \delta({\bf x}) \space \rm d^3 x$$ provided that ...
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### What exactly is moment? Why does it correspond to a rotation?

Wikipedia says: Moment is an expression involving the product of a distance and physical quantity. I don't quite get it. Moment is a vector, the cross product of the distance vector and the vector ...
317 views

### Moments by normal stress

I am a bit confused with the following formula why is that the normal stress ($z$), not the normal stress ($x$), is involved in the formula for the moment around $x$, $Mx$? Likewise, My also equals ...
1 vote
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### What is mass moment? [duplicate]

My teacher gave the following definition while teaching chapter "Center of mass": "It is defined as the product of mass of the particle and distance of particle from point about which ...
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### Does "moment" have a single meaning in physics?

I am a high school student and I am curious about the word moment and what it means in different contexts, whether it has a definite meaning or not? I know it has some relation to different kinds of ...
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### What are the proper definitions of moment, couple, torque, 'moment of force'?

When I read some scientific articles I am getting confused with the interchange being used between Torque, Couple, Moment, 'Moment Of Force'. Have I got this correct? Moment is supposed to be some ...
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### Is the angular acceleration of a rigid body independent of the reference point?

I'm solving this particular question (refer to image) in which a rod is released from equilibrium after one of the two springs to which it is initially connected is disconnected. In order to calculate ...
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### Why does the Larmor precession frequency depend on $\vec{B}$ instead of $\vec{H}$?

From what I know: The magnetic field strength, $\vec{H}$, is the field generated by a free current flowing on an electric conductor. The magnetic flux density, $\vec{B}$, is a response of the medium ...
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### Intuition behind First moment of area and link to centroids

I essentially have the same question, however only concerning the First moment, as this user ,however none of the answers satisfy my questions. I understand that we are trying to get a sense of the ...
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### A problem about moment (torque ) [closed]

Everybody knows that moment of a force increases with distance. However, there is a problem about it that makes me confused these days: Let's take a look at this picture due to the formula M = F.d, ...
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### Physical meaning of internal bending moment

Here's the setup: The textbook, where this is from, first walks through how to find the strain and stress as a function of z, which is fairly straightforward. Then, it calculates the "total internal ...
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### When calculating first moments of mass in cylindrical coordinates, can we use $r,\theta$ instead of $x,y$?
Usually when we want to find the center of mass of a 3D body, we need to find the first moments of mass about $x,y,z$, call them $M_x,M_y,M_z$. Defined by $$M_x = \iiint x\rho \ dV,$$ where $\rho$ ...
I'm having a hard time looking for the distance ($x$) on which the forces must be located for a maximum bending moment. The reaction forces in $A$ and $B$ are dependant of the value of $x$, and so ...